On the fine-tuning problem in minimal SO(10) SUSY-GUT

Abstract

In grand unified theories (GUT) based on SO(10) all fermions of one generation are embedded in a single representation. As a result, the top quark, the bottom quark, and the $\tau$ lepton have a universal Yukawa coupling at the GUT scale. This implies a very large ratio of Higgs vacuum expectation values, $\tanb \simeq m_t/m_b$. We analyze the naturalness of such a scenario quantitatively including all the relevant radiative corrections and find that in minimal unified supergravity models with universal soft supersymmetry breaking parameters at the GUT scale, the necessary amount of fine-tuning needed is excessive. GUT threshold correction to the universal Higgs mass parameter can significantly reduce the fine-tuning required for such large values of $\tanb$. We also point out that the top quark mass can play a crucial role in explaining the hierarchy between the SUSY breaking scale and the electro-weak scale and, hence, the naturalness of large values of $\tanb$.

20 pages, 10 figs, uses PHYZZX version to be published in Phys Rev. D

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Cited by in corpus (8)

• Yukawa Unified Supersymmetric SO(10) Model: Cosmology, Rare Decays and Collider Searches
• The Unified Minimal Supersymmetric Model with Large Yukawa Couplings
• Sparticle Mass Spectra from SO(10) Grand Unified Models with Yukawa Coupling Unification
• Naturally Heavy Scalars in Supersymmetric Grand Unified Theories
• Yukawa Unification as a Window into the Soft Supersymmetry Breaking Lagrangian
• Rescuing Grand Unification Scenario for Neutrino Mass
• Low-Energy Effective Lagrangian from Non-Minimal Supergravity with Unified Gauge Symmetry
• Comparatively Light Extra Higgs States as Signature of SUSY $\mathrm{SO}(10)$ GUTs with 3rd Family Yukawa Unification